Such policies actually do a wonderful job on discouraging travel to the extent when most people will no longer need any blanket ban to stay put. The sole thought that your destination might get onto the wrong list while you are there, sending you into the Mickey Mouse uncontrolled "self-isolation with exceptions" upon arrival, will make you think more than twice before booking. Whether the potential public health benefits of that outweigh the tremendous economic damage is quite arguable. I would instead be looking into something similar to the German setup - large-scale testing of those returning from high-risk REGIONS (not countries - regions!) instead of blanket restrictions on whole big chunks of the world, a huge part of which isn't any more dangerous than the UK in terms of contagion risk. But probably in a year or two we'll know more about who was right and who was wrong.